1. Field of Art
The present invention relates to a hitch control unit for use in a tractor.
2. Description of Prior Art
U.S. Pat. No. 5,231,892 discloses a hitch control unit for a tractor that comprises a housing having a pair of sidewalls joined to an outwardly convex cover wall formed with a fore-aft extending slot. An arm that can be moved manually along the slot is connected to a transducer, such as a potentiometer, that produces an output signal indicating the desired position of the implement mounted on the hitch of the tractor. An adjustable stop is movable by means of a thumb wheel along the slot and defines an abutment for the transducer arm. After the arm has been moved to raise the towed implement, for example while the tractor is performing a steering manoeuvre, it can quickly be returned to its position in abutment with the stop so that the towed implement can be returned to its original position.
The control knob on the end of the transducer arm, by which it is manipulated by the tractor operator, can be pivoted on the arm out of abutment with the adjustable stop to allow the arm to be moved intentionally past the stop when necessary.
In U.S. Pat. No. 5,231,892, the thumb wheel that adjusts the position of the movable stop is mounted on the housing for rotation about an axis parallel to the pivoting axis of the lever. This makes it necessary to use a complex linkage to couple the thumb wheel to the adjustable stop. Since the linkage includes meshing gears and a toothed thumb wheel, a smooth, infinite adjustment of the stop is not possible. As the thumb wheel moreover is spring loaded to restrain unwanted movement of the movable stop, the wheel always has to be pushed downward against the spring force and maintained in the downward position before rotational movement thereof becomes possible.
With a view to mitigating the foregoing disadvantage, the present invention provides a hitch control unit for use in a tractor. The unit comprises a housing having an arcuate surface having a tangentially extending slot. There is an arm extending through the slot and rotatably mounted in the housing. A transducer is connected to the arm to produce a signal indicative of the position of the arm along the slot. There is a stop movably mounted in the housing to define a reference position for the arm along the slot. Finally, an adjustment wheel is rotatably mounted in the housing to adjust the position of the movable stop. The adjustment wheel has an internally screw threaded bore and is mounted in the housing for rotation about an axis that extends parallel to the slot. The adjustable stop is connected to or formed integrally with an arcuate rack in screw threaded engagement with the bore in the adjustment wheel.
Another disadvantage of the unit of U.S. Pat. No. 5,231,892, is that the use of a pivotable control knob on the end of the transducer arm to allow the stop to be bypassed is costly to implement and inconvenient to operate.
In a preferred embodiment of the invention, the arm connected to the transducer is resiliently bendable in a direction transverse to the slot in the housing to allow it to be deflected around the abutment presented by the adjustable stop when it reaches the reference position.